riscv-pk: Set platforms properly

lib/systems/for-meta.nix

@@ -13,6 +13,7 @@ in rec {
   i686    = [ patterns.isi686 ];
   x86_64  = [ patterns.isx86_64 ];
   mips    = [ patterns.isMips ];
+  riscv   = [ patterns.isRiscV ];
 
   cygwin  = [ patterns.isCygwin ];
   darwin  = [ patterns.isDarwin ];

pkgs/misc/riscv-pk/default.nix

@@ -36,7 +36,7 @@ in stdenv.mkDerivation {
     description = "RISC-V Proxy Kernel and Bootloader.";
     homepage = https://github.com/riscv/riscv-pk;
     license = stdenv.lib.licenses.bsd3;
-    platforms = [ "riscv-linux" ];
+    platforms = stdenv.lib.platforms.riscv;
     maintainers = [ stdenv.lib.maintainers.shlevy ];
   };
 }